This invention relates to a method for determining petrophysical properties of a subterranean layer which employs both seismic data and log data.
It is well known to employ logs, such as wireline well logs, to determine valuable petrophysical properties associated with a subterranean layer of interest. Petrophysical properties, such as porosity, water or hydrocarbon saturation, and lithological composition (i.e. shale or sand), provide valuable information in determining the presence and extent of hydrocarbons in the layer of interest. However, such logs are very limited in a real extent to only about 6-12 inches around a borehole in which measure meets are taken. Moreover, obtaining logs such as wireline well logs can be time consuming and expensive in requiring drilling of a borehole for each such well log.
Petrophysical properties of a layer of interest can vary widely at different locations. Therefore, accurate determination of variations in properties over a large area of a layer are not practical by use of wireline well logs, since such determination would require many, possibly hundreds or thousands, of such well logs.
Seismic prospecting is effective in estimating depths to subterranean layers, and is cost effective in surveying a large area, but the resulting seismic data provides insufficient information to make accurate determinations of, for example, the extent and amount of hydrocarbons in a hydrocarbon-containing subterranean layer (hydrocarbon reservoir).